Gas turbine engines generally include a high pressure compressor for compressing air flowing through the engine, a combustor in which fuel is mixed with the compressed air and ignited to form a high energy gas stream, and a high pressure turbine. The high pressure compressor, combustor and high pressure turbine sometimes are collectively referred to as the core engine. Such gas turbine engines also may include a low pressure compressor, or booster, for supplying compressed air, for further compression, to the high pressure compressor.
Gas turbine engines are used in many applications, including in aircraft, power generation, and in ships. The desired engine operating characteristics vary, of course, from application to application. More particularly, when the ambient temperature is lower, the core engine can operate to output a higher shaft horse power (SHP) without increasing the core engine temperature to unacceptably high levels. On a hotter day, however, the core engine temperature may rise to an unacceptably high level if a high SHP output is being delivered.
To satisfy the demand for an engine which can output a high SHP even when the engine ambient temperature is high, e.g., on hot days, inlet system evaporative coolers or refrigeration systems which reduce inlet air temperature typically are utilized. It also is known to use water spray fogging devices to inject water into either the booster or the compressor. Such coolers or other refrigeration systems are used on hot days to cool the air supplied to the core engine and enable increased horsepower output.
Although coolers, refrigeration systems and fogging devices are effective in facilitating high power output from a gas turbine engine on a hot day, these known systems and devices also typically require water pumps, pressurized air for aspiration, and other components which increase the engine cost, including maintenance cost. In addition, such systems and devices require water clean-up.
It would be desirable to provide a gas turbine engine which is operable to output a high SHP even on hot days while the core engine operates at a level of low severity. It also would be desirable to provide such an engine which is not significantly more expensive, in both material and maintenance, than known engines, does not require significant water clean-up, and is relatively simple to operate.